Web tensioning mechanism



Nov. 23, 1965 R. 1.. BALLARD 3,219,247

WEB TENSIONING MECHANISM Filed July 29, 1963 United States Patent 3,219,247 WEB TENSIONlNG MECHANISM Reginald Leonard Ballard, Reading, England, assignor to The Berkshire Printing Company Limited, Reading, England Filed July 29, 1963, Ser. No. 298,066 Claims priority, application Great Britain, Sept. 12, 1%2, 34,803/62 2 Claims. (Cl. 226-495) This invention relates to a mechanism for tensioning a web of paper or other material running continuously through a machine and has been devised as a solution to the problem which arises with such machines of maintaining the web tension constant when, as may be necessary for cleaning or some other purpose, one of a pair of feed rollers has to be withdrawn from engagement with the Web.

This problem arises particularly with colour printing machines wherein it is vital that web tension is maintained whenever a particular impression roller is disengaged from the web otherwise when the machine is next used the colour printing areas will be misaligned.

According to the invention a web tensioning mechanism comprises a pair of pivoted elements each coupled to a separate roller and rigidly connected together, one of said pivoted elements being movable on release of its associated roller from the Web to displace the other pivoted element and its associated roller by an amount sufficient to compensate for the release movement of the first roller and maintain the web tension constant.

A particular embodiment of the invention as incorporated in a gravure printing machine is illustrated by Way of example in the accompanying drawing which is a side elevation of the web tensioning mechanism.

Referring now to this drawing the Web W normally travels along the path indicated by the arrows. It thus successively travels around a roller 1 Whose position is fixed, between a printing cylinder 2 and an impression roller 3 and around a movably positioned tensioning roller 4.

The impression roller 3 is mounted upon an eccentric 5 Which can be turned in a frame to raise the impression roller 3 oil the web.

The eccentric 5 is embraced by the forked end of a bell crank lever 6 which is angularly movable about a fixed pivot 7 and has a slot 8 formed in its upper end. Adjustably secured in this slot by locknut 9 is one element of a ball coupling Whose other element 10 is attached to the end of a push rod 11 whose other end is attached to the element 12 of another ball coupling whose other element is secured by a locknut 13 to a slot 14 at one end of a link 15. This link 15 is angularly movable about the axis of a pivot pin 16 rotatable on a fixed bracket 17 and fiXed to parallel links 18 which carry the tensioning roller 4 between their other ends. The provision of the ball couplings at the ends of the push rod 11 permits of lateral adjustment of the impression roller or of the unit comprising the printing cylinder and the impression roller.

When the impression roller 3 is raised the lever 6 moves slightly anticlockwise causing push rod 11 to move to the left and links 15 and 18 to move anticlockwise the web W and the parts then assuming the positions indicated by the dash lines. The result of this action is that there is no reduction in the tensioning of the web W when the impression roller 3 is released the upward movement of the latter being compensated by the leftward movement of the tensioning roller 4.

The mechanism may be adjusted either by altering the effective length of the push rod 11 the ends of which are screw threaded into the ball coupling elements 10 and 12, or alternatively by altering the position of the ball coupling elements along one or both of the slots 8 and 14. If necessary all these expedients may be used.

I claim:

1. In a printing machine of the kind in which a Web runs continuously and at constant speed between a printing cylinder and an impression roller, a shaft for said impression roller, a web tensioning mechanism comprising a web tensioning roller, a pivoted bell crank lever means having a forked end embracing said shaft of the impression roller, means for Withdrawing said impression roller, a second lever means pivotally linked at one end to said tensioning roller and a rod pivotally connecting the other end of said bell crank lever means and said second lever means so as to cause displacement of the second lever means and the associated tensioning roller in a direction and by an amount sufiicient to compensate for a release movement of the impression roller away from its printing cylinder and maintain the web tension constant.

2. In a printing machine having a web tensioning mechanism as claimed in claim 1 and the other end of said bell crank lever means having a slot therein, a first ball coupling adjustably connecting one end of said rod to said other end of the bell crank lever means and including means cooperatively related with said slot, said second lever means having a slot therein and a second ball coupling adjustably connecting the other end of said rod to said second lever means and including means cooperatively related with said second-mentioned slot.

References Cited by the Examiner UNITED STATES PATENTS 1,978,715 10/1934 Meisel 10l228 2,570,773 10/1951 Davis 226- X 2,714,268 8/1955 Battey 24275.3 X

ROBERT B. REEVES, Primary Examiner.

RAPHAEL M. LUPO, Examiner. 

1. IN A PRINTING MACHINE OF THE KIND IN WHICH A WEB RUNS CONTINUOUSLY AND AT CONSTANT SPEED BETWEEN A PRINTING CYLINDER AND AN IMPRESSION ROLLER, A SHAFT FOR SAID IMPRESSION ROLLER, A WEB TENSIONING MECHANISM COMPRISING A WEB TENSIONING ROLLER, A PIVOTED BELL CRANK LEVER MEANS HAVING A FORKED END EMBRACING SAID SHAFT OF THE IMPRESSION ROLLER, MEANS FOR WITHDRAWING SAID IMPRESSION ROLLER, A SECOND LEVER MEANS PIVOTALLY LINKED AT ONE END OF SAID TENSIONING ROLLER AND A ROD PIVOTALLY CONNECTING THE OTHER END OF SAID BELL CRANK LEVER MENS AND SAID SECOND LEVER MEANS SO AS TO CAUSE DISPLACEMENT OF THE SECOND LEVER MEANS AND THE ASSOCIATED TENSIONING ROLLER IN A DIRECTION AND BY AN AMOUNT SUFFICIENT TO COMPENSATE FOR A RELEASE MOVEMENT OF THE IMPRESSION ROLLER AWAY FROM ITS PRINTING CYLINDER AND MAINTAIN THE WEB TENSION CONSTANT. 